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991.
Young-Woo Ok Min-Gu Kang Donghwan Kim Jeong Chul Lee Kyung Hoon Yoon 《Current Applied Physics》2009,9(6):1186-1190
We fabricated point-contacted a-Si:H(p)/c-Si(n) heterojunction solar cells using patterned SiO2 and investigated their electrical properties using the light current–voltage (I–V) curve and Suns-Voc measurements. The light I–V curves showed bias-dependent changes according to the applied voltage in the point-contacted cells, especially in the samples with a long distance between the point-contacted junctions. The Suns-Voc measurements showed that the bias-dependence of the light I–V curves did not originate from the recombination in the SiO2/Si or a-Si:H(p)/c-Si(n) interface, but from the series resistances. It is possible to explain the bias-dependent light I–V curve in terms of the conductivity of a-Si:H(p) and difference in the electrical contact properties between a-Si:H(p), ZnO and c-Si(n). These results mean that the electrical properties of the a-Si:H(p) layer and the contact properties with this layer are also critical to obtain a high Jsc and fill factor in n-type based Si heterojunction solar cells. 相似文献
992.
We considered an extension of the standard functional for the Einstein–Dirac equation where the Dirac operator is replaced by the square of the Dirac operator and a real parameter controlling the length of spinors is introduced. For one distinguished value of the parameter, the resulting Euler–Lagrange equations provide a new type of Einstein–Dirac coupling. We establish a special method for constructing global smooth solutions of a newly derived Einstein–Dirac system called the CL-Einstein–Dirac equation of type II (see Definition 3.1). 相似文献
993.
Jagannathan Narasimhan Kazuo Nakajima Chong S. Rim 《Discrete Applied Mathematics》1999,90(1-3):195-221
In this paper, we consider the yield enhancement of programmable structures by logical restructuring of the circuit placement. In this approach, an initial placement of a circuit on the array is first obtained by simulated annealing on a defect-free array. To implement the circuit on a defective array, the initial placement is reconfigured so that only the defect-free portion of the array is used. Customizing a given initial placement for each defective chip by logical restructuring, if done very fast, would be a cost effective method for yield enhancement. We describe a formulation of the circuit reconfiguration problem in terms of graphs and pebbles, wherein each processing element (PE) of the array is represented by a vertex which is classified as either defective or nondefective, depending upon whether the PE that it represents is defective or nondefective. Vertices representing PEs that are physically adjacent are connected by an edge, whose length is a measure of the proximity of the PEs. The logic elements of a circuit are represented by weighted pebbles. The initial placement of the circuit on the array corresponds to an initial placement of the pebbles on the vertices of the graph, with at most one pebble per vertex. The problem is to successively shift these pebbles along paths in the graph, such that after reconfiguration no pebble is located on a defective vertex, and an associated cost function is minimized. We describe four cost measures using weighted displacement and weighted shift of the pebbles. After presenting exact algorithms for some special cases of the problem, we prove the NP-completeness of the general cases of the corresponding decision problems. 相似文献
994.
Bae Soon Son Sam Jin Kim In-Bo Shim Bo Wha Lee Chul Sung Kim 《Hyperfine Interactions》2006,169(1-3):1285-1290
The cation distribution and magnetic structure of Cu x Fe1?x Cr2S4 (x?=?0.1, 0.2, 0.3, 0.4, and 0.5) has been studied by X-ray and neutron diffraction, vibrating sample magnetometer (VSM), and Mössbauer spectroscopy. The charge state of Fe is found to be ferrous (Fe2+) for the x?=?0.1 sample; ferric (Fe3+) for the x?=?0.5 sample; mixed state (Fe2+, Fe3+) for the x?=?0.2, 0.3, and 0.4 samples. The Mössbauer spectra of the x?=?0.1 sample show asymmetric line broadening, which is considered to be due to the Jahn–Teller effect of Cu2+ ions, and a symmetrical six-line pattern is shown for the x?=?0.5 sample. The valence state of the Cu ions for the x?=?0.1 and 0.5 samples is found to be divalent and monovalent, respectively. The magnetic structure of the samples was determined to be a ferrimagnetic structure with antiparallel alignment of the Fe and Cr ion magnetic moments. 相似文献
995.
Mohammad Rezaul Karim Chul Jae Lee Mu Sang Lee 《Journal of polymer science. Part A, Polymer chemistry》2006,44(18):5283-5290
Conducting polythiophene (PTh)/single‐wall carbon nanotubes (SWNTs) composites were synthesized by the in situ chemical oxidative polymerization method. The resulting cablelike morphology of the composite (SWNT–PTh) structures was characterized with elemental analysis, X‐ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared, ultraviolet–visible spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis, X‐ray diffraction, and transmission electron microscopy. The standard four‐point‐probe method was used to measure the conductivity of the samples. Field emission scanning electron microscopy and transmission electron microscopy analysis revealed that the SWNT–PTh composites were core (SWNTs) and shell (PTh) hybrid structures. Spectroscopic analysis data for the composites were almost identical to those for PTh, supporting the idea that SWNTs served as templates in the formation of a coaxial nanostructure for the composites. The physical properties of the composites were measured and also showed that the SWNTs were modified by conducting PTh with an enhancement of various properties. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5283–5290, 2006 相似文献
996.
Jong Su Kim Yun Hyung Park Sun Myung Kim Jin Chul Choi Hong Lee Park 《Solid State Communications》2005,133(7):445-448
The temperature dependence of emission spectra of alkaline earth ortho-silicates M2SiO4 (M=Ca, Sr, Ba) doped with Eu2+ ions is investigated. Two emission bands of Sr2SiO4:Eu2+ show the normal redshift with broadening bandwidth and decreasing emission intensity as an increase in temperature. On the other hand, emission bands of Ca2SiO4:Eu2+ and Ba2SiO4:Eu2+ show the anomalous blueshift with increasing temperature. For Ca2SiO4:Eu2+ and Ba2SiO4:Eu2+, the temperature dependence of the emission color can be described in terms of back tunneling from the excited state of low-energy emission band to the excited state of high-energy emission band in the configuration coordinate diagram. Our phosphors have a promising potential as phosphors for green or greenish white-light-emitting diode pumped by ultraviolet chip. 相似文献
997.
Chan Sik Cho Na Young Lee Tae‐Jeong Kim Sang Chul Shim 《Journal of heterocyclic chemistry》2004,41(3):409-411
3‐(2‐Aminophenyl)‐1‐arylprop‐2‐yn‐1‐ols are readily converted to 2‐arylquinolines in good yields in ethanol at 80° in the presence of potassium hydroxide via domino isomerization and cyclization. 相似文献
998.
Boo Rim Choe Hyungwoon Koo Young Joo Lee 《Transactions of the American Mathematical Society》2004,356(5):1727-1749
We obtain characterizations of (essentially) commuting Toeplitz operators with pluriharmonic symbols on the Bergman space of the polydisk. We show that commuting and essential commuting properties are the same for dimensions bigger than 2, while they are not for dimensions less than or equal to 2. Also, the corresponding results for semi-commutators are obtained.
999.
Hyperfine Interactions - Al substituted CoAl x Fe1?x O4 (x=0.1, 0.2, 0.3, and 0.5) have been studied with X-ray and neutron diffraction, Mössbauer spectroscopy and magnetization... 相似文献
1000.
Hyejun Jung So Yeoun Kim Kangseok Lee Byung H. Lee Sang Eun Shim Soonja Choe 《Journal of polymer science. Part A, Polymer chemistry》2005,43(16):3566-3573
A novel bifunctional vinyl‐terminated polyurethane macromonomer was applied to the dispersion polymerization of styrene in ethanol. Monodisperse polystyrene (PS) microspheres were successfully obtained above 15 wt % of macromonomer relative to styrene. The steep slope from the reduction of the average particle size reveals that the macromonomer can efficiently stabilize higher surface area of the particles when compared with a conventional stabilizer, poly(N‐vinylpyrrolidone). The stable and monodisperse PS microspheres having the weight‐average diameter of 1.2 μm and a good uniformity of 1.01 were obtained with 20 wt % polyurethane macromonomer. The grafting ratio of the PS calculated from 1H NMR spectra linearly increased up to 0.048 with 20 wt % of the macromonomer. In addition, the high molecular weights (501,300 g/mol) of PS with increased glass transition and enhanced thermal degradation temperature were obtained. Thus, these results suggest that the bifunctional vinyl‐terminated polyurethane macromonomer acts as a reactive stabilizer, which gives polyurethane‐grafted PS with a high molecular weight. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3566–3573, 2005 相似文献